Wildlife Species Guide

Opossum

Description

Opossums are a member of the order Marsupialia, a primitive group
of mammals found most commonly in Australia. Kangaroos, koalas and
wombats are other wellknown marsupials.

The Virginia opossum is among the most primitive and
generalized of marsupials. Its closest relative is the CentralAmerican opossum. An adult opossum is 2 to 3 feet long and
weighs between 4 and 12 pounds. It has an elongated snout, a
pink nose, black eyes and prominent, naked black ears. Its head
is usually white and its coarse body fur is mostly grayish white
but tends to be darker on its legs.

An opossum is well-adapted for climbing. Its feet are plantigrade
(shaped so the opossum walks of the sole of its foot with
the heel touching the ground) and its toes are dexterous (skillful,
like fingers). Its hind feet have a toe that resembles a thumb and
makes them look somewhat like human hands. Its naked, scaly
tail is able to wrap around and grasp limbs and can support the
animal's full weight for short penods.

The opossum's skull has 50 teeth, the highest number found
in any mammal.

Prior to the European settlement of North America, the Virginia opossum
was found only in Central America and the southeastern United
States. During the 1900s, its range expanded northward and
westward. Its northern distribution is limited by winter temperatures and
its western distribution is limited by dry, hot climates.
The opossum has been introduced along the Pacific Coast and is
currently found from southern California to southwestern British
Columbia.

Extreme southeastern Nebraska was part of the opossum's
presettlement range and it is now common in southern and
eastern Nebraska. In the Sandhills and Panhandle, opossums are
restricted to major drainages such as the Loup, Niobrara and
North Platte rivers.

Opossums and raccoons share similar habitat requirements and
both species use similar areas in a similar manner. Good opossum
habitat includes a combination of large trees and shrub thickets,
abundant water and crop fields. An opossum will den nearly anywhere
that is dry, sheltered and safe, such as the abandoned dens of other
animals, hollow trees and logs and brush piles. A nest of leaves and grass
is usually made at the den site. An opossum will use a number
of dens within its home range.

Habits

An opossum is primarily nocturnal (active at night)
but may become diurnal (active during daylight hours) during
cold weather. An adult male's home range is about 250 acres and
tends to shift through the course of its life, while the adult
female's home range is smaller, about 125 acres, and is more
permanent. An adult male is solitary, while an adult female is
with her young through most of the year. The young of the first
litter begin living on their own away from the nest when they are
three months old, but second-litter young stay with the mother
until the following spring. Litter-mates may share common dens
for up to three months after separation from their mother.

An opossum does not hibernate, but remains inactive for short
periods during severe winter weather. However, its energy reserves
are not as extensive as those of a raccoon, so it must forage
on a regular basis, even during extreme weather conditions.

An opossum is a very slow runner and will try to escape
predators by climbing the nearest tree. When cornered on the
ground, it initially exhibits a threatening posture, hissing and
making low growls. If attacked, it generally lies very still as if
paralyzed or dead, a habit called playing possum. It also emits
a foul smelling substance when threatened.

An opossum does not have a method for storing
food or energy and needs food sources that are stable from season
to season and year to year. Its diet includes a wide variety of
foods, including insects, earthworms, small mammals, fruits,
grains, plants, and the flesh of dead animals it happens to find.
It forages intensively in a small area on whatever is available.
When food resources become depleted in one place, the animal
simply moves to a new area.

Although the foods an opossum eats are varied, they must be
abundant and closely spaced. Extreme weather conditions, such
as a severe drought or extended cold, can reduce food availability
and have devastating effects on opossum populations.

Reproduction

A female opossum usually has two litters per year. Mating occurs in
mid-January through February and continues into August. Young
partially-developed opossums are born 13 days after mating. They
migrate to the female's pouch where they continue to develop for
several weeks. The young emerge from the pouch when they are
1 l/2 to 2 months old and ride on their mother's back. They are
weaned at three months. The adult female mates again soon after
the first litter is weaned, and the first litter disperses within
one month of weaning. Young from the second litter are weaned and
on their own by September or October.

There are 8 to 10 young in an average litter, but litters of 17
have been reported. The young are capable of reproducing at six
months of age, but usually don't until the year after they are born.

An opossum is short-lived and has high mortality rates at all stages.
Mortality of young still in the pouch ranges from 10 to 25 percent. Of
those that survive through weaning, fewer than 10 percent live longer
than one year. The oldest known wild opossums were 2 l/2 to 3 years old.

The most important mortality factors are caused by humans,
predation, parasites and disease, exposure and starvation.
Human-caused mortalities include hunting, trapping and highway collisions.
Important predators include great horned owls, dogs and coyotes. An opossum
is a host to a multitude of internal and external parasites including
intestinal worms, fleas and ticks. These generally are debilitating and
increase susceptibility to diseases and malnutrition. An opossum is
highly resistant to rabies.

Opossums seldom cause problems for homeowners, ranchers or farmers. They
sometimes raid trash cans or dog food containers, but these situations
are easily remedied by denying access to the containers.

The opossum is classified as a furbearer in Nebraska but is
not taken in large numbers by hunters or trappers, and its pelt has
little value. Opossum furs are primarily used to trim inexpensive
cloth garments.

From 1941 to 1989, over 350,000 opossums were taken by
fur hunters and trappers. Harvest totals from 1980 to 1989
indicate an average annual harvest of 11,900 opossums valued
at $7,200. From 1984 to 1989, only 42 percent of the harvested
opossum pelts were sold.

The uniqueness of the opossum intrigues scientists and nature
enthusiasts. It is the only marsupial in the United States. In
Australia and elsewhere, marsupials have been out-competed
and even driven to extinction by more modern mammals. Yet,
the opossum has adapted to the changing environment in the U.S.
with its simple manner, and continues to thrive.